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CPSC 875 John D. McGregor Architecture evolution.

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Presentation on theme: "CPSC 875 John D. McGregor Architecture evolution."— Presentation transcript:

1 CPSC 875 John D. McGregor Architecture evolution

2 Implementation should be changing faster than the architecture But both will change because – Requirements change – Product goals change – New patterns are discovered

3 Types of Maintenance Adaptive – Add new features – Add support for new platforms Corrective – Fix bugs, misunderstood requirements Perfective – Performance tuning Preventive – Restructure code, “refactoring”, legacy wrapping, build interfaces

4 Lehman’s Laws 1.Continuing change — An E-type program that is used must be continually adapted else it becomes progressively less satisfactory. 2.Increasing complexity — As a program is evolved, its complexity increases unless work is done to maintain or reduce it. 3.Self regulation — The program evolution process is self-regulating with close to normal distribution of measures of product and process attributes.

5 Lehman’s Laws - 2 4.Invariant work rate — The average effective global activity rate on an evolving system is invariant over the product lifetime. 5.Conservation of familiarity — During the active life of an evolving program, the content of successive releases is statistically invariant. 6.Continuing growth — Functional content of a program must be continually increased to maintain user satisfaction over its lifetime.

6 Lehman’s Laws - 3 7.Declining quality — E-type programs will be perceived as of declining quality unless rigorously maintained and adapted to a changing operation environment. 8.Feedback system — E-type programming processes constitute multi-loop, multi-level feedback systems and must be treated as such to be successfully modified or improved.

7 Eclipse Launched in 2001 Eclipse Foundation 2004 Over 170 companies Almost 1000 committers Originally ran on Linux and Windows Now a dozen platforms

8 Plug-ins A plug-in is a jar with a manifest : : :

9 Extension points =

10 Add a menu item


12 Views and perspectives View – presents specific information in a manner that speaks to a stakeholder Perspective – an arrangement of views, editors that are related

13 Eclipse 3.0 Plug-ins were to be replaced by a new component model – OSGi bundles This was the new runtime architecture Chose Service Management Framework (SMF) as the framework implementation Provided a compatibility layer for existing plug-ins

14 OSGi bundles An OSGi bundle runs in a container It is possible to start, stop, and pause actions in the container without restarting the entire container Can have more than one version of a module running at the same time.


16 Bundle has Activator package com.javaworld.sample.helloworld; import org.osgi.framework.BundleActivator; import org.osgi.framework.BundleContext; public class Activator implements BundleActivator { public void start(BundleContext context) throws Exception { System.out.println("Hello world"); } public void stop(BundleContext context) throws Exception { System.out.println("Goodbye World"); } }

17 Bundle has Manifest Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: HelloWorld Plug-in Bundle-SymbolicName: com.javaworld.sample.HelloWorld Bundle-Version: 1.0.0 Bundle-Activator: com.javaworld.sample.helloworld.Activator Bundle-Vendor: JAVAWORLD Bundle-Localization: plugin Import-Package: org.osgi.framework;version="1.3.0"

18 OSGi container An OSGi container allows some classes in some bundles to be visible OSGi has its own class loader so no need to maintain a separate one

19 Bundle life cycle Supports lazy activation which can be either an advantage or disadvantage.

20 Rich Client Platform People were using Eclipse – which was intended to be an IDE builder as an application builder. To support the RCP modules had to be reconfigured. They were split to narrow the functionality that had to be loaded.

21 RCP an Platform after reconfigure

22 Dependencies

23 Feature.xml %description %copyright %license

24 Features Features contain features Features contain bundles

25 P2 as a solution for updates

26 p2 P2 uses installation units Meta-data describes artifacts Artifacts are the building blocks Profiles allow user to pull from the repository the installed units at a point in time

27 Eclipse 4 4 was another major build Goals: – Simplified programming model – Attract new committers – Take advantage of new web technologies

28 Eclipse 4 Separation of model from generation of the view Eclipse 4.0 uses dependency injection to provide services to clients. Dependency injection in Eclipse 4.x is through the use of a custom framework that uses the the concept of a context that serves as a generic mechanism to locate services for consumers. The context exists between the application and the framework. Contexts are hierarchical. If a context has a request that cannot be satisfied, it will delegate the request to the parent context. The Eclipse context, called IEclipseContext, stores the available services and provides OSGi services lookup.

29 3.X -> 4.x getViewSite().getActionBars().getStatusLineManager().setMessage(msg); @Inject StatusLineManager statusLine; statusLine.setMessage(msg);

30 Acyclic Design Principle No cycles in a design Not even indirect cycles

31 Stable Dependencies Principle If A depends on B the B should be more stable than A


33 Here’s what you are going to do Complete one mission thread for robotic surgery Assume that over the next 3 years the types of surgery done by robots will expand. Write a brief report that identifies the parts of your architecture that will have to change as new surgeries are added. Describe how it could be designed NOW to handle the change THEN.

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